I changed my oil a few days ago and there is a leak coming from around the drain plug. When I first did the oil change I only screwed in back in by hand so I wouldn't strip the thread. The next day I saw it was leaking so I tried tightening it by hand more and then used a wrench the rest of the way. It is still leaking and I don't know why. I am 99% sure it is coming from the drain plug so could it be its not on the threads correctly? Please help.
Multiple causes are possible:
If there's a gasket or washer between the drain plug and the engine sump, the gasket or washer may have been deformed or damaged.
If there's no gasket or washer, and one is supposed to be there, whatever's supposed to be there is missing.
If no gasket is required, the face of the drain plug and/or the face of the sump may have been damaged, such that oil can seep through what should be flat, mating surfaces that seal.
You may have cross-threaded the drain plug, and the resulting damaged threads do not now seal.
In any case, remove the plug (catching and saving the oil for reuse), clean and dry things off, and examine the pieces. Serious cross-threading may have damaged the threads sufficiently to require a threaded insert to repair the female threads in the sump, and/or replacement of the plug.