First yoga related injury after 17 years of practice ?? Help !

Good morning.

I will attempt to keep this question to the point.. I have been practicing bikram yoga off and on for 17 years now, most recently 4 days a week. Ironically I came to bikram style to rehab an old foot fracture which has since healed incredibly and helped thru my practice. Without the standing balancing postures I am not so sure I would have had such great success in my rehab. Yesterday in class I did NOT feel as warm as I normally do ( ie: hot and sweating) by the time we came to standing head to knee, but I felt strong, mentally and physically. FIrst set I did my basic warm up set.. no head to knee , second set I went for it.. and that is the scene of the crime.. left leg standing head to knee, as soon as I went to put the head to knee.. I felt a sharp pain down my low back just over the buttock and in to the butt cheek ( I think) the pain brought me to my knees and there I lay till the class was on the floor at which time I tried to get up during their savasana. I did not want to disturb the class.. but I was seeing stars and literally could NOT get off the floor..the teacher assisted me, although he asked me to stay and lay still thru the rest of the class, I insisted to leave so I could try to get comfortable with ice and anti inflammatory .. since being home, I am able to move a bit better but forward bending is excruciating and sleeping well, just uncomfortable. Im on ice now .. I am sure its temporary and will go away with rest, but.. how long do I wait until my next class? and what can this be? Is it related in any way to my going to the gym ( i ironically just started the gym this week too 3 days.. working with light weight)..Help..?? Any advice and or suggestion is appreciated.