The doctor at urgent care said my 21 month old has infantigo, would this cause bumps with hard knots under the skin to th point that he doesn't want to stand on that leg?

See a doctor: Impetigo is a bacterial infection on the surface of the skin. It is usually treated with a topical antibiotic ointment. Hard lumps under the skin, with pain, may be abscesses. This is a bacterial infection under the surface of the skin, which requires oral antibiotics and a possible procedure to open the skin and drain the infection.