Dear Liam,
It sounds like you didn't fully ground the attunement. Did you follow all the instructions and take a full hour?
If not, you should go back and go thru it all again being sure to direct the energy down below your feet into the earth.
If you did follow all the directions, I'd still recommend going back and doing it again as maybe you just need some more time to fully integrate the mahatma attunement. Maybe your solar plexus is needing a little extra time too.
It is common during attunements for some to feel different sensations like you describe. It is not your imagination but it is not anything to be concerned about either. Feelings and sensations are normal in most forms of energy work. :-)
Much Love, Light & Mahatma healing,
SkyDancer