I have not idea what you are talking about - I can not visualize a "skin mass", that sounds bad but could be nothing but a sore.. how big, hard or soft... other description material may help.
Best to take the dog to the vet if the situation has not already improved.
Hi Helen,
There is really only one way to deal with this, and that's not to try and treat it yourself or guess what it is/isn't.
Go and get the "skin mass" checked out with a vet. Let's hope it turns out to be nothing much to worry about. Or even if she needs it removed, that doesn't have to be a terrible thing.
My dog once needed a lump removed from her lip, and biopsied.
It turned out to be an infected hair follicle. It never came back, but left a tiny scar on her lip where it had been taken off.