First of all, you cannot do any alteration on cheque handed over to you by him..This will make the instrument "void'"....
I would advise you to consult a local lawyer equally....
Lack of agreement happens when u trust people & they betray / backtrack with your finances....
You can opt a few steps:
1. Send a legal notice..See how d person reacts..
2. Did he did have any verbal quarrels wid u or did he refuse in wrting to u...all these things also add to ur evidences..
3. u may attempt criminal proceedings (private complaint / FIR) in form of breach of trust/ cheating....but i dnt suggest cheque bounce case..if u attempt criminal proceedings, there should be some strong elements like:
- that u have some police complaint against him in past wrt same matter or
- he has threatened you IN PUBLIC PLACE OR IN PRIVATE or
- he has refused in writing that he has taken that much money from you or
etc......You maybe aware of other details which i do not know
4. lastly u can attempt civil proceedings but that will be more expensive as u need to pay court fees on entire amount
Feel free if i can be of any help to you...Even i am handlng court issues on my own....Only if u r active, other person will bend & you need to be equally paitent to see results of your legal actions.