Welcome to the board Weimy1206.
A vet visit would be in order for your dog, given her age and the fact that there is a mushy lump there. As long as it's not growing from day to day, you don't need an appt tomorrow, but next week would be good. If you see obvious changes from day to day, though, it would be a good idea to get her in this weekend if possible.
I hope it turns out to be nothing!