If a single spot has stuck around more than three weeks, it's probably not a pimple — common culprits are a sebaceous cyst, milia, a closed comedone with a stubborn keratin plug, or, less often, a basal cell carcinoma if it's on a sun-exposed area and crusts or bleeds. A nodular cyst can persist for four to six weeks even with treatment. Stop picking, stop layering actives. A dermatologist can extract a sebaceous cyst in a 10-minute office visit or inject a deep nodule with cortisone for a 24- to 48-hour flatten. If it's been over six weeks, gets the right diagnosis — patches and benzoyl peroxide won't resolve a structural lump.