What trick does Huck play on Jim? Why is he tricking him now when he didn’t want to before?

Huck kills a snake and puts it by Jims foot so that when he wakes up he will freak out. The only problem is that when a snake dies, the mate will find it and curl up around it. This happened and it resulted with Jim getting bitten by the snake. Jims foot swelled up really bad but eventually went down with proper treatment. Huck decided to trick him now because they are friends now and he felt like it was okay to trick him and not be racist because they're friends.