Darn it! Expensive mistake?

[Fatboy123]

I was using a 26cm Mauvel stainless steel frying pan to sear some chicken thighs for lunch. It was spitting a bit so I grabbed the lid from a 24cm Le Creuset and placed it on the frying pan as I don't have the official lid.

2 minutes later and lid seems to have sealed to the frying pan...... bummer, bummer.... bummer.

It's now completely cold but still won't separate. Anyone have any ideas?
Any advice greatly appreciated!

 

[Fatboy123]

Thanks guys.... to my great relief I got it off.

I unscrewed the knob and poured some water in the hole. Heated the pan with a tea towel over the hole and as the pressure grew steam started coming out of the sides. Rushed it to the sink and gave the underside of the pan a whack with a mallet. Second whack and the lid came off.
Flipping 'eck will be more careful next time!