I don't know what the bumps are, but I do know that the pictures are not of a satsuma leaf. They are Trifoliate Orange, Poncirus trifoliata, or one of its hybrids used as rootstock for citrus.
I think you will find these leaves are different from the original plant, and grow from low down below the graft point. They should be cut off flush with the main trunk or they will take over.
You should ask locally about those bumps!

good catch citrange, yea cut those branches off now, before it over takes the "good" graft.

look at the leaves on the upper trunk, are they bumpy too? a pic of the whole tree and one of the lower trunk would be helpful.

Aha, at first when it started growing I thought it might be the root stock, but it was higher up than I expected (I thought it'd be almost growing out of the soil) and then I saw articles about not pruning "the skirt" of the tree (and I kind of felt sorry for it) so I left it. But now that you mention it, the leaves do look different from the top.

There's been no new growth on the top though, so I haven't really compared it (also no bumps on the top leaves, but it might be because there's been no new growth).

Thanks a million! I'll go chop it off when I get home.