Fir 324,325, 114, 506 - who is responsible for witness

There is a case of fighting. Yet not chargsheet is filed. I had fracture on right hand and also blood comes out at that incident. Now police ask me for witness then only they will file charge sheet. Now who is responsible for witnesss. On erp sheet / government hospital record sheet it is written assault by iron rod and fracture. 1)Does medical certificate is enough for this or witness is necessary. 2) who is responsible for witness complainant or police.