Hi, I have gone through your medical history carefully and understood your concern. The hard and movable lump you notice above the left clavicle could be a swollen lymph node. Tdap shot is followed by a series of events that will help providing the desired protection. Lymph nodes are also involved. That could be another explanation especially if you noticed that lump after the Tdap shot. In either case, I highly recommend to consult with your primary doctor first for a good clinical examination. He/she will judge if you need further diagnostic tests after clinical examination. Hope this helps. Dr.Albana