Core strengthening. Exercises that strengthen the core can be helpful in maintaining integrity and reduce stress on the spine. Typically disc herniations will resolve on their own as soon as 3-6 weeks or as late as 6-9 months. Just depends on how you take care of yourself, exercise, anti-inflammatories, tylenol (acetaminophen) and if you need to lose weight that will help immensely.
Try Local Treatments. Icing your back-laying on your side until the area where the spasm is better.You can also use some anti-inflammatory meds like Ibuprofen 600 to 800 mg up to three times a day for a couple of days.Watch for stomach/gi problems. Don't combine with Aspirin which could increase those chances. You may need a short course of skeletal muscle relaxants or even opioids like lortab. See a dr. If not better.
Stretching & NSAIDS. I would start with heating up the buttock area that is affected. Then lie on your back, knees bent. Place ankle of affected leg on opposite knee and pull that knee toward chest. You should feel a pulling sensation of affected buttock. Do this several times 3x daily. Also i would suggest taking an otc anti inflammatory such as Motrin or aleve (naproxen). A good message would help too.