Hello, welcome to HCM forum. There are several reason that can cause black spots on the tongue. Practically without inspecting visually it is almost impossible to predict the correct diagnosis. A good picture may also help. But most common black spot on tongue which is of a pea size along with similar spot around it could be suggestive of black hairy tongue . It is simply the elongated growth of the papillae present over the tongue and discolored by food stain and bacterial growth. Some times the elongation is so much that it looks like a bunch of hair over the tongue, hence its name. it is generally caused by some illness, some medicine intake and mostly due to some local constant irritation. Interestingly intake or using mouth wash containing MENTHOL for long time is one of the local factor of developing such condition. Which could happen in your case as you were taking Altoids (peppermint/menthol) for long time with one side. Doctor prescribed iron tablets because iron deficiency is also sometimes blamed for this kind of condition. Antibiotics generally does not cause this condition until taken for long time at a stretch. Anyway, the condition is self limiting but may take time to regress. Continue your iron tablet, stop Altoids. Maintain your oral hygiene with proper brushing. keep your tongue clean gently using a tongue scraper or using your tooth brush. Do not use any commercial mouthwash, warm salt water mouth wash can be used instead. Hope your problem will be relieved soon. Good luck.