Wink and Timmy(soon to be something else) go at it a lot. Timmy is 2 months older than Wink and a lot bigger, and he uses his "mitts" to hold her, she growls, hisses and spits and appears to be very upset. These "fights" are rough! Usually, she ends up clamping down on Timmy's leg or ear, and he takes off. Almost immediately, she starts hunting him and ends up jumping on him, or he jumps on her, and the process repeats endlessly. Sometimes, they are both yelling like they are being killed, and the first time it happened, I thought Timmy was hurting her, but the only one that ever bled was Timmy, who got bit on the foot, and she would almost instantly "attack" and I figured out their fights weren't real fights. Yesterday, Wink was screaming like she was being tortured and I went into the bedroom they were in to check on her and they were laying on the bed, licking each other as if nothing happened. After I went to bed, they went out into the living room for a while and I heard her scream a couple of times, and about the time I was starting to get concerned, she came in and got in bed with me and a few minutes later, here he comes, and they went to sleep all bunched up together, so she's just being very vocal when she plays.
If your cats aren't actually doing damage, I wouldn't worry too much.