What could be the possible explanatons for a lump around the anus?

Hemorrhoids: Hemorrhoids are the most common cause. A hemorrhoid is a bulging vein around the anus. When you strain such as with heavy lifting, constipation or child birth, the vein can dilate so much that it does not snap back into its normal shape. Then you can get a clot in the bulge which makes it last even longer. If the bump does not resolve, go see your family doc to make sure it is not something worse.

Many possibilities: If it developed quickly and is painful, then a thrombosed external hemorrhoid or peri rectal abscess is likely. If it developes after bowel movements and then resolves, a prolapsed internal hemorrhoid may be the problem. Something that has developed slowly could be anything from an anal tag to anal warts to anal cancer. See a physician if it persists.