the one on your arm might be a cyst if it's a lump sticking out of your arm that doesn't really hurt then it probably is. If it is that then go to the hospital and they will probably refer you to a doctor who will drain it for you. I'm not quite sure of the one on the armpit
If it's the size of a pencil eraser and red it's probably an infected oil gland. If it's the size of a large grape then I would suggest some type of bacterial infection. Lymph nodes swell and become very painful, especially when pressed. My first thought would be Cat scratch fever. I know that sounds odd but there really is such a thing and it is usually caused by a cat scratch. Either way you will probably need some antibiotics. I was wondering where on your arm the other nodule is. Keep in mind it could be something else entirely.
There are other posts on here that may help you as well. It could be anything from a swolen lymph node to a clogged pore. Is it like a pimple or more like a mass?