i will try to take some better pictures in day light, the colour of the bumps are same as the rest of the coin and looks like its part of the coin metal. Also some thinness can be seen on the reverse at that point.
If this coin has a sunken in area on the reverse side directly opposite this area then someone has probably pushed something into the reverse side to create the raised area.if there is no sunken in area then your coin may have a die chip.
This was a common error on the dateless Twenty Pence coins, according to "Coin World" the blobs were caused by a die collapse. I got one in my change and sold it for £50
What the heck is "die collapse"? I know what die sinking is from improper hardening, but I have no idea what "collapse" is. And when a die sinks from improper hardening it doesn't have sharp defined edges like the OP coin does.
