My opinion is keep showing your home, as your agent has 72 hours before the listing status has to change to "contingent: which ends most showing chances for all practical purposes. If you get lucky and there is a better offer, you can try to cancel the deal by objecting to all the buyer requests in attorney review. The window for this is narrow (assuming the buyer's agent demands a signed contract and also confirms the listing designation change), so good luck!
If you need to move forward right away, keep showing it and see if you can get a backup offer. What do you know about your buyer? Are they solid buyers with a pre-approval? What are the financing terms? There's a lot to consider. If you play you're cards right you should be able to get your buyer to increase their offer BEFORE you sign...
In my state it is customary and expected to take "Back-Up Offers"...
as a matter of fact, it is Highly Encouraged.
In this current market, don't let any potential Buyer get away!
If you have a Listing Agreement with a Real Estate Broker, ask them.
If not, you need to see what your Contract says.
If you are not certain, ask a Real Estate Attorney.