Help with bunny injury

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2MB, 2448x3264px

Having trouble bonding two rabbits. One (call it bun A) was being submissive up to now when it started humping the supposed dominant bun (bun B).

After separation we noticed the top of the two scraps of fur, having a small sliver of flesh. It was very concerning and we scowered for the wound on bun A (the only one with white) and could not find anything. Not only that, bun A acted just fine.

Another fight happened after bun A escaped her pen and humped bun B again. Floating in the water dish was the significantly more concerning hunk of flesh in the picture. Again, searched long and hard and cannot find an injury on either rabbit, and both are acting normal. I really want to find the wound but bun A will not hold still long enough for a really thorough exam.

I used a square of toilet paper and rubbed her down and still no spots of blood or any cries from touching an injury. Is this hunk of flesh worrying enough to go to the vet to assess the damage? Any advice would be helpful.