You can use a bike tyre repair kit. The best way to determine whether you have a tyre puncture and its location is to remove the tube from the tyre, inflate to double the normal tube size and submerge in water. Mark any places on the tube where bubbles emerge. You can repair these holes using a standard tube repair kit. Check the inside of the tyre for any dirt or sharp items that are lodged in the tube and remove if found to help prevent future punctures.
If you find that there are no bubbles that emerge, then ensure that no dirt is trapped in the valve by refitting the tube in the tyre and inflating and deflating several times to help push any trapped dirt out of the valve.