If a creditor put a hold on my checking account and my paycheck was deposited into that account, what can I do?

Unfortunately not much unless you can show that the funds are in some way exempt from garnishment or levy on the account.  When you say that the creditor put a "hold" on the account do you mean that they have a judgement and they filed it with the bank to levy the funds in the account? Then you may have to go to court to file something regarding the judgement -  possibly vacate a default or if your state allows certain exceptions to garnishment under which the money falls then you could also file for that - and you need to also check with the bank what they need as they may have other forms to fill out.  You need to come to some sort of agreement with the creditor to have them release the hold in order to be able to have the paycheck money available to you.  Otherwise, this will continue to happen.  Good luck.

Also the filing of the bankruptcy may indeed stay the execution of the garnishment or levy but it appears that it has already taken place and that they may have the money needed.  If it is more than was in the account the hold will stay until the judgement is fulfilled.  You can get some relief but you need to move quickly.