u/16-1-24-20-15-14

I brought one of my gerbils out of the tank to let him roam around for a bit, and i noticed a weird spot at the base of his tail. Upon closer examination, it seemed to be a pinkish, swollen bald patch, and the skin was bleeding a bit in some places. I unfortunately do not have any pictures, as he is quite skittish and doesn't like being held down. He didn't seem to be in any pain, I accidently brushed the area with my finger when I was moving his fur to get a closer look, and he didn't flinch or anything. He lives alone now, as his brother attacked and severely injured him a few months ago, (poor boy is missing some toes now :[ ) and I just switched their enclosures, so he is now in the larger tank that his brother was in before, and I've seen him a lot less lately, despite him previously being quite social. (I don't know if that's helpful or relevant...) Should I take him to the vet?