1 tiny mole on my arm has changed slightly, now a slight bump instead of just totally flat, still v. Small and doesn't itch but should I be concerned?

GET BIOPSY=be safe. To be safe: any mole change should be biopsied. Change could include: color change, increase in size, bleeding, starting to itch. Signs of melanoma are: assymetry of lesion, indistinct borders, colors red-black, size >1cm.
Mole. A changing mole, in this case one that is becoming raised may or may not be indicative of skin cancer. See a dermatologist for evaluation.