lump under skin

Hey mamas couple of days ago my almost 7 months baby girl had her 6 months shots ( we did them kinda late ) and I noticed a lump under her skin she doesn't have pain cuz I massaged a little bit and it's not red but it's feels like a peas , I did research and some people said it's normal but another said it's bad and to call the doctor , should we call the doctor or it's that normal ? She had before same shots but never that lump under the skin