You need to have this looked at promptly. You might have developed an abscess or blood clot in the area you injected into.Or something in the oxycontin pill itself could have caused local damage. Pills have different sorts of fillers that keep them together that could potentially cause damage to the skin or blood vessels. Also injected an oxycontin could be extremely dangerous. Oxycontin is a slow release drug- the 80 mg is meant to be slowly released over most of the day when you take it as directed. If you put the whole dose into your body all at once by injecting it, you could overdose and die quickly. So you were lucky in a way to have missed. But get this lump looked at right away so it is properly treated. Hope this helps.