CO2 gas...you bottled a little too soon. Plan ahead, pull the cork, decant it and let it 30-45 minutes.. or plug the bottle with your thumb and give it a good shake...like shaking up a Coke when you were a kid...release the CO2.
The gas wants out, that's why you see the bubbles. Help it out.
Next batch, take your time and it will degas all by itself...think months not days.
I made this mistake my first batch too. No idea what degassing was. I did the thumb plug and shake over and over method. It was pretty miserable and took a long time. Hope there's another way around that for you.
Might want to keep an eye on those bottles as well. Had my first experience this summer with cork cannons. Couldn't figure out what that noise was while we were in bed one night until the morning when I saw the mess in the cellar. It didn't take much to uncork the remaining bottles. Pretty much once I pulled the plastic sleeve, the cork shot out and the volcano started.