I had situation like that few years ago, also from sneezing...what helped me back there was rest for about 10 days, with very little spine movement,mostly lying, and some pain killers/relax drugs. It was very frustrating not being able to do anything, but I think it's the best you can do if you're not medical expert, because you can worsen things :(
This happens to me frequently. I do stretching, use a heated wheat bag and an acupressure mat. If this doesn't help I use a painkiller gel on the affected area.
For stretching I lie down on a yoga mat and slowly turn my head to the right. I relax my neck and let the weight of my head pull it further into the stretch without forcing it. I rest in this position for a few minutes and then gently return to starting position. Repeat on the left side. Make sure you're not getting cold lying on the floor. Keep warm all the time and avoid draft because it might make it worse. Get well soon!