Seeking credit while you're applying for a mortgage is not the smartest move. The inquiry will cause a small hit on your score, and your score will get hit again then the new account shows up. Depending on where your score is, it could cause an negative impact on your interest rate (if you move from the "Excellent" band to the "Very Good" one, etc)

I'd hold off on seeking any new credit until after you close. Why take a risk on your house?