I had punched a classmate and gave him a black eye who was abusing my parents when i was 15. what charges can be filed against me?

how old is the matter.              

First do not be disturbed with your own doubts, sparked by others, and never repeat the same, as it may seal your further career in Govt Jobs.  Police have many jobs to do, and they may at the most call you and your parents to PS, warn or give a slap to please the complainant, get an apology letter from you without registering a complaint.  Be careful in the future and do not be provoked by others, have your emotions under control as you have stepped into teens now.

Hello sir, greetings of the day.
As per your query, there are laws against verbal harassment as well as against for punching someone in Indian Penal Code.

Section 294 of the Indian Penal Code lays down the punishment for obscene acts or words in public. It states that whosoever causes annoyance to others, and does any obscene act in any public place, or sings, recites or utters any obscene song, ballad or words, in or near any public place, would be punished with imprisonment of for a term which may extend to three months, or with fine, or both.
Section 352 of the Indian Penal Code lays down the punishment for assault or criminal force otherwise than on grave provocation. It states that whosoever assaults or uses criminal force on any person shall be punished with imprisonment which may extend to three months or with fine or both. 
Also section 358 of Indian Penal Code defines assault or criminal force on grave provocation. Whosoever assaults or uses criminal force on any person on grave or sudden provocation done by that person must be punished with simple imprisonment for a term of one month or fine or both.
These are the sections of Indian Penal Code which can be filed against you and the verbal abuser. 
Hope this solves your query.
Regards
Nirali Nayak
Law Student

@Nirali:  The queriest is also a student like you, and appears to be sensitive and was worried about the repercussions.   All these sections/punishment only the other party goes to Police Station and complain it.  A considerate SHO, even he is sadist/unkind,  never registers such a complaint, Please avoid quoting sections and punishments, as such sensitive persons during depression may frighten further and may want to escape from......

There is no case registered agaisnt you.

If at all they wanted to file a case against you they could have done it long ago when you were 15 years old then and not as an adult now, especially when you have already completed your school education and even might have completed the college education or being employed as this stage.

As no action taken by the school authorities or by the parents of the schoolmate at that time, there is no case maintainable at this belated stage.

God bless you , your parents and teachers. Mr.Shailesh.

Since you got involved in the fight with your classmate when you were 15 years old, there's no way that you'll be facing any issues with the matter.

The school coordinator would have mentioned about "Police" to you in order to scare you off such that the situation isn't repeated, but there's no way police is going to take any action against you for fights like these (especially due to age factor). Moreover, such fights do take place among boys during school days and it's not a big deal, and it is the responsibility of school administration to handle such issues and not police.

So be sure, there's no problem that might come across your way for such a fight in school.

Hope It Helps

Regards
Kevin M. Paul

not stated how old is the mtter