Sailfing tang has given himself blunt force trauma

[MarsOnBars]

My sailfin was fine this morning, and I come home and his lip is hurt, Popeye in one eye, and not swimming properly. I don’t know what to do in this situation, please help!

 

[MarsOnBars]

The tang is still eating and chasing at the nori I put in. I don’t think it’s chemical related as the other two in the tank are acting as usual. All measurements appear usual