Lumbar back strain or sprain?

Ok, so i believe this happened from a single event of a heavy deadlift at the gym. obviously my form was perfect but what i have now is a very stiff lower back when i try to stand up or sit, i dont have pain wile moving around only when bending forward or doing any kind of lifting that mimics the deadlift ( i.e. bend over rows). i can however still squat? which i thoughts was weird but any how, i would like to know if this is a common injury or something els, and what i can do to get it better and how long should it take to heal up fully. its been about a month or so now already. P.S. i also dont have any mussel spasms or anything like that and no tingling up or down my back or legs