About releving letter

sir, i worked in a non registered engineering projects doing institute for 8 months and left that job due to salary problems. now i got selected in bank and so i have asked the employer for releving letter. he is refusing to give me that letter because his institute is not registered what to do know sir i am getting tensed will it create problem to my bank job because i had mentioned this 8 months experience in application. i don't know what to do please suggest me what to do