Go for a walk.
Talk to a friend.
Let your friends give you platonic affection. Like hugs and stuff.

It depends what you like to do. I was single for 5 years, intentionally, after leaving an abusive relationship.

I rekindled my love of horses, went to concerts with other single friends, started beading/making necklaces, started taking an exercise class, scheduled regular sessions with my counselor. I went on a cruise, by myself.

It sucks, but you will get through it.