I think I have liquid reteining, one of ny finger on my foot is big and red and it hurts when I walk or just touch it. What should I do?

Cellulitis/Infection. If a single toe is red, painful and swollen, it it likely an infection. See your Doctor or go to an Urgent Care for evaluation ASAP. Elevate the foot and use heat (ie heating pad at low setting, or soak the foot in warm soapy water and then elevate if your appt is within 12-24 hours. I would recommend being seen today, if possible.
Need to be checked. Fluid retention would be unusual in a healthy 23 year old and wouldn't likely only involve one toe. Its will be important for you to get checked for fracture, infection, arthritis or gout. A visit to your doctor would be the best course of action.