The past participle of the verb bite is bitten in both American and British English (e.g., “You could see the teeth marks where her baby brother had bitten her”).
In American English, you can also use the past participle bit (e.g., “Cal had bit down hard on a peach pit and broken his tooth”).
Bit is also used as the simple past tense of “bite.”
You can use the QuillBot Grammar Checker to make sure you have the correct past tense of bite or any other verb.