I just had a red bloch in the shape of a triangle appear on both the upper and lower side of my arm with red dots in it should I be concerned?

Yes. Any abnormal skin lesion, rash or mole should be checked out by your doctor or dermatologist.
You did not... You only provide info on how it looks, not on size or how it feels! if present for a few days, you should have it looked at! a picture is worth a thousand words. Good luck!