First apply a cold compress, containing ice if possible. A cold compression (e.g. crushed ice or a packet of frozen peas) is invaluable if applied as soon as possible for 15-20 minutes. Apply a crepe bandage and give the sprain plenty of rest until all discomfort has subsided. Further strain will inevitably lead to further swelling and a longer recovery period. If matters do not improve after a few days, consult your doctor as s/he may wish to refer you for physiotherapy.