Hi, I can understand your concern for the pimple like thing on left forearm. There can be multiple of the possibility of the bump. In my opinion it appears to simple folliculitis. I suggest you to apply antibiotic cream application because are best effective in these condition. You can apply fucidin cream or mupirocin cream over the affected area. Do not pinch, pop or scratch or even touch the area unnecessarily as it can cause aggravation of the rash. Wear cotton clothes and cotton inner garments which will give a soothing feeling to the skin. Stay away from extreme of environment such heat and humidity. Take care.