Looks like it's an external AC-DC adapter. Generally these should get warm with use. Is it too hot / warm to tough with your bare hand? It should consume @ 44-48 Watts, the power supply for these seems to be able to handle 48 watts. (No overhead, kind of dumb?)
I just bought a 4k LG monitor a few days ago and in the process of cable managing it, I noticed that the power brick is getting pretty hot. I have no reason to believe it'll ever get too hot to touch, but it is by a wide margin warmer than any other power bricks I have around. The monitor doesn't...
Make sure there is some room around the adapter (nothing covering it) and that it's not lying on something that would insulate it (carpet).
My current and previous main monitor have external bricks that get warm after some time. The previous monitor was going on about 5 years of use but I don't think there was any real sign of it "wearing out" or anything.
As long as it's not getting so hot you can't touch it for more than a few seconds, it should be fine.