First time BIAB overshot temp - what should I expect?

I am doing my first BIAB today on my kitchen stove. I have done many all grain brews using a cooler mlt and batch sparging out doors using a turkey fryer.

I put in 7.5 gallons of water, some ph 5.2 and turned on the heat. When the temp was 105*, I added the grains and stirred. I kept stirring every few minutes while it was coming up to temperature and then got distracted by something - by the time I got back it was at 165* (ranging from 161 - 170 depending on where the temp probe was. I quickly turned off the gas and stirred to try and get the temp down but it was hanging very nicely in the 158 - 165 range for 20 minutes or so. I added a handfull of ice cubes to help get the temp down but it was still very high for a long time.

The recipe is a belgian blond with a 15.75 lb grain bill of which 1 lb is sugar. So I have 14.75 pounds of grain with 7.5 gallons of water. It is still on the stove with the heat turned off and after an hour it is now down to the low 150s.

Is there anything I should do besides continue on? Should I expect a higher than normal FG? Problems with foam or head retention?

You'r e still within mashing temps. You'll still make wort. It will potentially reduce the amount of fermentability so the final gravity is a bit higher. Say 1.022 instead of 1.014. It will still make beer. I don't think mash temperatures affect head retention.

At 170 you may start extracting tannins from the grain and start the mash out phase stopping the grains from converting. Hard to say since it was only 20 minutes and there was a range of 158-170. Just have to wait and see. Odds are you should be ok...it didn't get that hot...if you were over 170 I would be worried.