What is this bump on my dick?

it seems to get smaller and it is painless and it feels a little hard and it dont give out anything and idk what it is can u help

picture?

Is this about garden pea size - if so, can you push it inwards towards the main body of your penis? Also, if you can do this, does the bump take a second to fully reappear, or is it there immediately you release pressure?
Yes, a picture or two would help …