The IRS only allows one person to use the Head of Household (HOH) Filing Status per household. The person filing as HOH should be the one who paid over half the cost of the household, even if by $1. Check out the TurboTax FAQ regarding the qualifications for claiming HOH below.
At this point, your fiance's return is not going to be accepted with the HOH status until you Amend your Tax Return to change your filing Status to Single. Click this link for instructions on How to Change a Tax Return You Already Filed.
Your Fiance will need to mail his tax return in if using HOH, it will not go through electronically.
https://ttlc.intuit.com/replies/3288637