It hinges on the nature of the relationship you have with this guy that you work with.
Assuming you are expecting more out of what happened than he is prepared to give, such as romance, you have a problem and have made a mistake.
A coworker who slept with you for the fun of it isn’t looking for romance.
So, it is contingent on how the two of you are looking at this.
Many people sleep with their coworkers.
They do so for varied reasons.
They wanted intimacy without romance.
They did it to get back at another coworker.
They do it to ingratiate themselves with this coworker and establish better business connections.
They do it while out at happy hour one night, getting drunk, and gaining the liquid courage to take a chance at it.
There are varied reasons.
You have to figure out what your reason was and be candid with yourself about it.
This is where the complexity sets in.
When you have to be candid with yourself about your reasoning behind sleeping with a guy you work with, it’s tempting to tell yourself a whole lot of lies.
You attempt to mask what your true intention or reason is.
You tell yourself that you didn’t do it for this or that reason.
You force yourself to believe that it never happened.
Listen, in the end, this was done for a distinct reason.
You had a motive in all of this.
You have to figure out what that was.
The moment you are conscious of your reasoning behind why this happened, the easier it is for you to tell whether you made a mistake by sleeping with this guy that you work with.
You are going to be around this guy at work and bound to engage with him in some capacity.
Even supposing you don’t work in the same department, you are fated to cross paths with him from time to time.
The last thing you should want is an awkward work environment.
This would make it that much harder for you to go to work or do your job effectively.
This affects you mentally and isn’t wise.
The sooner you come to terms with the nature of your relationship with this guy, the better.
If you are interested in this guy and want more out of the relationship, tell him so.
Let him know that you want to get to know him on a romantic level.
The sooner you put this out in the open and let him know, the easier it is to resolve this and move forward.
Ask him out on an official date or tell him how you feel about him.
On the flip side, if you don’t want anything more out of this and see no romance in the future, let him know that as well so that he doesn’t get his hopes up.
Do not procrastinate.
The longer you wait, the more confused and anxious you are.
You don’t want to constantly come into a work environment that is tense.
This makes it stressful for you to do your job to the best of your ability in such an environment.
In such an environment, you would now be risking your value at the job and this would only create more unnecessary work-related issues.