Hello Erisoluse and 
I think mick1271's theory could well be correct.
However, I also wonder if it could be bubbling caused by corrosion of the steel under the copper plating. 1p and 2p coins minted since 1992 have just a thin layer of copper over a steel core. I've seen coins where the copper layer has been damaged and they look similar to yours. It could possibly be due to a defective planchet.

I think mick1271's theory could well be correct.
However, I also wonder if it could be bubbling caused by corrosion of the steel under the copper plating. 1p and 2p coins minted since 1992 have just a thin layer of copper over a steel core. I've seen coins where the copper layer has been damaged and they look similar to yours. It could possibly be due to a defective planchet.