What to do about a painful fatty corpuscle?

There's a lump on my back that my previous doctor told me not to worry about, so I'm pretty sure it's not cancer. After I moved a bunch of heavy furniture the other day, however, it started to hurt. It seems to have widened out but become less prominent in shape. It's not unbearably painful, but it does produce a pretty persistent aching feeling. Is it possible such a thing could burst under my skin from stress or something? Has anyone had an experience like this? What should I do about it? Thanks.