ICE IT! I am a veteran of such episodes and always applied heat. Finally in my 50's I learned from a young lawyer in my office whose wife was a physical trainer and whose dad in Italy was a professional soccer coach, that initially, heat just adds to inflamation. After a couple of days applying ice for abut 20 minutes at a time several times a day, then use the heat alternately with the ice. Gradually resume walking. Once you are recovered take up an exercise routine that strengthens you core. If you have a gym nearby employ the aid of a certified trainer who can teach you the moves. I can tell you from my own experience that's the long term secret to avoiding the hassle of such spasms.
Jane