If it' s a paw paw, it will smell similar to a banana. It will have a couple large seeds in it as well. The ones on my farm are green and then turn a light yellow and then the coons and deer eat them up. It may be some type of plum. I have several wild plum trees and they are purple after falling off and the trees are grayish with flaky bark. They are usually about like a quarter in size though.