Woke up to sensitivity in my armpit, theres a red dot, surrounded by sensitive reddish and swollen area, just on lymph node. spider bit? what to do?

Not a bite-infection: This is not likely to be a bite. It is more likely a gland or hair follicle that has become infected. Use warm packs and topical antibiotic ointment twice a day. If it is spreading or worsening go into be seen to make sure you don't have an abscess that needs to be drained.

Observe: A single, isolated red spot is suspicious for insect bite or maybe inflamed hair follicle. Redness & swelling is your body's normal reaction to any insult/injury. It would be very unlikely that this would be something poisonous requiring immediate action. You can watch it: if the redness and/or swelling advances dramatically or if you develop any fever, rash, other symptoms, see your provider.