Delamination on bottom of softboard

Hi guys,
I left a Greco 9ft softboard in my room during the recent British "heatwave" and have come back to a couple of hand sized bubbles on the underside of the surfboard. How do I go about fixing this? The plastic is quite thin on the underside of this board.
I left a Greco 9ft softboard in my room during the recent British "heatwave" and have come back to a couple of hand sized bubbles on the underside of the surfboard. How do I go about fixing this? The plastic is quite thin on the underside of this board.