I had a colonoscopy a week ago been irritated around anal area ever since, what can I use.?

Balmex and fiber. Get back on a regular diet with plenty of fiber and water. Gently cleanse the perianal area with a mild soap and pat dry. Use balmex (yes, what's sold for babies bottoms) on the perianal skin to help the skin heal. You are aiming for a stool that is formed but deformable- not hard, not smeary. Use premoistened wipes (not baby-wipes) to cleanse until healed. If not better, see your doctor!
COLONOSCOPY RASH. This is not an uncommon reaction. Warm water compresses 3 or 4 times a day; no toilet paper for a week (just use warm compresses over the area; after the compresses use either zinc oxide ointment or butt-paste. No hot, spicy foods for a week. Be patient.