dont worry excactly the same happend to me last summer i didnt played the bass for 1 month and when i had the practice session for 2 hours 2 massive blister apeared next day in my right hand fingers!!! I was in pain for 1 week and after i was playing, my leather fingers come back to normal and i noticed the following:
1 not playing for long time brings that to surface
2 always in band rehersals i play harder than home
3 practicing daily is solving that and more technique issues
4 always warm up before you play