There are two possibilities here: 1: you are still under warranty and if that is the case I would start with the retailer you purchased from to seek a remedy. 2: if you are not under warranty, if there are lumps in the mattress it could be from shifting quilting material or from the foam wearing out and developing impressions where your body pushes in the most.

If it is in fact out of warranty, you are not going to have much luck rejuvenating the mattress. Both potential reasons for the lumps are not things you can fix. You could try a topper, but if the lumps are caused by impressions in the foam, the topper will merely follow those lumps as well and create a softer, but still uneven, mattress.

Try the warranty and contact the retailer option first. Good luck!

It depends on what you mean by a lump. If you mean the lump in the center of the bed (where no one ever sleeps) than just start sleeping in the center of the mattress to even it out. If you mean a random lump where you sleep than I agree with Joe it is time for a new mattress.

Good luck.