If you've signed a contract, you have a problem. Now, contracts are written and contracts are broken- and if you've truly changed your mind, you need to see what the repercussions of breaking the contract would be.
Many contracts stipulate what damages
will be if a contract is breached. So your first step is to read through and see. If there is no mention, likely the buyer can sue you for actual damages- including whatever they have spent in furtherance of this transaction (attorney, title, etc.) but also including what it would cost your buyer to buy something similar. If there are 100 houses for sale that are similar to yours in your area and the buyer can purchase one of them for the same price or less than you agreed, you are fine. If they have to pay more, damages will include that differential, i.e., what they will have to pay, minus what they were paying you. If there is something special about your house that will make it difficult for them to replace, that will also be taken into account.
They can also sue for specific performance, which means to force you to go through with the contract, which courts may grant, unless you have a really good reason and the buyer can be compensated monetarily.
I guess the big question is will the buyer actually spend the money to hire a lawyer and proceed to sue you. The answer to that question is "no" more often than not.
But those are the possibilities.
Good luck. If you have more questions, please reply. Otherwise, kindly click the green "Accept" button. Best wishes.