Hi.. Welcome to HEALTHCARE MAGIC.. As per your complain and presentation of symptoms it seems like bug bite or insect bite itself and the size increased as there must be more of toxic poison released from the stinger that might have embedded in the skin and the allergic reaction that has caused with the poisonous chemical has led to th increase in size of the lump. Nothing to worry about it, you can take anti-allergic medications like Levocetrizine or diphenhydramine [benadryl] for relief from the itching,pain and redness. Apply a steroid based Ointment over the lump for reducing inflammation. Do cold compresses over the bump. Try and avoid scratching the bump when it itches to avoid infection.. It can take around one to two weeks for it to resolve completely.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora.