Big air bubbles in insulin vial

I filled a reservoir of insulin pump and after that big air bubbles formed on the top of the vial.

Is it safe to use this vial with insulin next time?

You got back pressure it should be fine.

When you fill reservoir with insulin, did you first insert air into the vial? This is typical to do, so after insulin is drawn out it replaces the space where insulin was. If you put in too much air or took out less insulin, the extra air causes the bubbles.