What tissue of yours was injured? When I look up 'sprain' it is a ligament injury. If a Dr diagnosed sprain, what is the healing time for a sprain? Research the healing time of injured tissues. Tendons have a long healing time to get up to their best healed strength. They go through several stages in healing.
CharlieFedererer used to post very informative healing timelines that showed time vs strength. Since tennis often caused the injury in the first place and tennis strokes focus stress on the same location of the original injury, going back to tennis too early could be especially bad. Was your injury related to tennis? You injured yourself 6 weeks ago at Thanksgiving. I don't know the healing time for ligaments but for tendons I think 3 months is a very minimal time and I don't believe that the strength was that good at 3 months. Get advice from a well qualified Dr on what to do and when.
I had shoulder surgery March 29, 2017 to repair a full thickness, small tear of the supraspinatus tendon. The first 6 months of physical therapy were low stress to restore the range of motion of the shoulder joint while healing. At 6 months after surgery, strength training begins. Back slowly to normal begins after the nominal 'surgery recovery time' of 9 months, in Dec 2017. The healed tendon tissue is a scar tissue and is not as strong as the tendon tissue before the injury.
I played platform tennis twice about 2 weeks after the original injury. I decided it was not right and stopped playing. I believe that by playing I risked tearing the undiagnosed tendon tear farther.
The Health and Fitness Forum is more likely to have similar threads on thumb injuries.