If you're tire is just a little low on air pressure then nothing will usually happen when you drive the vehicle on low tire pressure.
But you may notice some handling differences in the vehicle and if the tire is really low on air pressure it could lead to a blowout because the tire gets stretched too much and then at high speeds the tire could come apart and blowout.
I would recommend going to a shop or somewhere else and get the tire pressure checked and have them inflated to the proper air pressure because it will make the vehicle more safe as well as improve your fuel mileage.