Injured my neck/back during workout, what should I do?

I was doing military press with dumbells last night and after I completed the last set I felt some pain in my lower neck/back on the left side. Into the evening it just began to hurt more and stiffen up. I put a heat pack on it and took some Advil. This morning it is even more stiff and continues to hurt, mostly when I turn my head. Will heat, rubbing and advil be enough over a few days or does this require a trip to the doctor? How long should I wait to do military press again?