Weird bump near the paw

I just noticed this weird bump near my dog’s back paw, and I was wondering if anyone had any idea what is it. He doesn’t seem in too much discomfort, he just licks it every now and then and doesn’t want me to touch it but he doesn’t limp. He’s a maltese, 10 years old. He spends a lot of time in my garden outside. Earlier my grandma gave him a bath, maybe he hit his leg but I’m not sure. Any idea? Thanks in advance.