Hello. It also happened to me once. With my vacu-hanger. I used the sleeve and it slipped exactly like you described.
What I did : I made a pause and didn’t touch it. Usually, in other places, I use to break blisters. But I let this one alone. Don’t break it. You don’t want it to infect.
I’m not very comfortable with the constriction sleeve, so I don’t use it anymore. I do prefer a little fluid buildup in the glans than a blister.
So,to sum up. Don’t break your blister. The water under the skin is here to help healing.
If it has broken, apply regularly some antibiotic cream, and try to keep the place clean and dry.
I hope it will heal quickly. Mine was 0.5 cm in diameter, at the very tip, and it healed within 10 days. Hope you don’t see your girlfriend or have a date before it heals.
05/2006 : 15cm BPEL X 12,5cm EG => 11/2006 : 17.5 cm BPEL X 13.5 cm EG => 5/2007 : 18 cm BPEL X 13.5 cm. 2 years later : shrank a bit : 17cm BPEL 01/2011
Really satisfied with my gains, but a little more flaccid would be nice. Would like to be a shower ;)
And most important : Girlfriend satisfied for about 3 years :)