Yes, you can.
You can insert a retainer into your nose piercing after 2 weeks. But, it will be always good to avoid retainers until your piercing is completely healed. If you can wait for at least 4 weeks after getting pierced.
Subsequently, can you pierce your ear with a plastic stud?
Plastic earrings, particularly medical-grade, are ideal for newly pierced earrings because they are hypo-allergenic. A lot of people are allergic to metals such as nickel, gold, and other alloy metals and therefore need something compatible with their skin, especially when it’s newly pierced ears.