‘I done it’ is grammatically incorrect but is used by many native English speakers in North America in very informal, colloquial situations.
The reason it is grammatically incorrect in this sentence is that ‘done’ is the past participle of the verb to do, to use the past participle we need to use an auxiliary verb to form a perfect tense or the passive voice.
- The player has done a lot for his team.
- The students were exhausted by the time they had done the last exam.
- The report was done by the accountant.
The correct way of writing the sentence would be to use the present simple tense or the past simple tense of the verb ‘to do’.
- I did it (yesterday/last week/last year)
- I do it (every day, routinely, normally)