It's very easy to add a box for an outlet in the same stud bay as existing electrical, but you want to be careful that you don't nick the romex stapled to the stud when you do it.
Alternatively, it works, the easiest thing you can do is swap the switch for a combo switch/outlet. Need to break the tabs so that the switch doesn't control the outlet (detailed in the instructions). Here's an example:
LinkAnother option would be to replace the single gang box with a double gang box. None of this is difficult, but you want to be confident you know what you're doing.