This is what's called a "pulled groin." Like you guys mentioned, after a week it feels like the injury has healed, until you move just right and realize it's not healed at all.
Groin pulls happen all the time in sports. In my experience it takes around a month to heal fully. The problem that I usually "feel" better about 2 or 3 weeks into recovery, try something too intense/stressful, and re-aggravate the injury.
You can try to ice you adductor, do whatever stretches you can, and take some ibuprofen or whatever. Also, you can try to massage/foam roll/ART your inner thigh. If the strain is bad enough, you may actually be able to feel a lump or adhesion in there. Work out the kinks to return the muscle to its full length, and relieve the pulling down there.