I would suggest you to show it to a skin specialist as rash
is not the cause of pain. I think pain is due to pulled muscles. I would advice you to avoid bending forward and lifting heavy weight. Also take myoril or myospaz for pain relief. A pea size nodule in your axilla
is a enlarge lymph
node. It is present normally also but enlarge in infection. So I think you should not be worried about this.