Sore on Cat's Lip and Moody Behavior

My partner and I's kitty has a sore developing on her lip. When I got home from work today he expressed concerns that she was acting moody and then mentioned the sore. I've never seen a sore on her like this and it appears to bother her but not enough to stop her from eating and drinking. Does anyone have any thoughts? Thanks so much!!

Looks like a rodent ulcer which can be due to a virus or a food allergy. Would be worth taking her to the vet for a check.