The word "in" in the sentence "I got a good hit in during the first two minutes" means "during" or "within." In other words, the speaker got a good hit on their opponent within the first two minutes of the fight. The speaker hit their opponent during the first two minutes of the fight. This means that the hit happened before the two minutes were up. You could also use a simpler word like "during" instead of "in." For example, you could say "The speaker hit their opponent during the first two minutes of the fight."