Someone knows what this is

My dog Wilson didn't have this bump this morning. When I got back to work he had this big bump on the side of his nose. He doesn't les me touch it, he still eat normally. Seems a bit low on energy.

He always had a lot of allergies but that doesn't look like it.

Already have an appointment tomorrow for that matter but it stresses me out.

Do you have any idea what this is ?