Hello, thank you for using Petco Pet Education Center, formerly Petcoach. I am sorry for your concerns about Rocky. This appears to be a small cystic nodule, probably not cancerous, but all lumps & bumps should be evaluated by your veterinarian. A small sample taken with a very small needle can be examined under a microscope to see if there is anything to be worried about. You can watch this for a while, but if it suddenly should enlarge, please have it looked at. Take care.