My finger is swollen and purple what can I do?

Swollen finger. If this is the result of trauma, typically the best thing to do initially is rest ice compression and elevation (rice). And then see a doctor to assess the degree of injury i.E is there a fracture. If it's not trauma related, one would need a further evalluation as to whether you have some vascular/circulation issue or possibly infection. Regardless, best to get a consult.
Go to your md . A swollen finger that is purple implies vascular change there are many causes some very serious so quit looking for this venue and go to a professional.