Hi runner1,
Based on your description of symptoms, a meniscal tear sounds like one of the more likely diagnoses. Many of these settle well with conservative measures including appropriate physiotherapy treatment / guidance, rest from aggravating activities especially twisting / weight bearing / squatting, flexibility and strengthening exercises and a gradual return to activity. Anti inflammatories / regular icing can also be useful in the initial 72 hours. Be aware that the meniscus does not have a very good blood supply which subsequently slows healing. In the event that appropriate conservative measures fail, surgical review for a possible arthroscope is usually the next line of treatment.
Hope that helps and good luck,