If you are not in an energy surplus, then you have no worries about dong this. The body needs to be nourished, and if your workout warranted it, no reason not to.
If you are worried about staying lean, as many of us are, myself included, you may proceed like this instead of an all out bulk. You apparantely are at or close to maintenance calories at this point if I am reading in between the lines correctly.
Start on an intelligent additon to create a caloric surplus. In other words, if say 2500 calories is your maintenance, increase by 300 calories per day. This will give 2100 extra calories per week. It takes approx. 3500 calories to make a lb., so in under 2 weeks you will be adding this.
You can start it with protein if you like. Simply adding 3 scoops of protein per day to your normal intake will typically add approx. 300 calories per day. This will start a small calorie surplus.
Do this for a few weeks, however you choose to add 300 calories, and see what happens. Then if you decide to, at some point as you gain this calorie amount will now become your maintenance calories, another increase is in order. Of course, the cleaner the additions the better.
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