bent or deformed finger can be of two types .reversible [corrctable] and non reversible types.reversible types can be evaluated by physical examination .these types of deformities can be corrected by physiotherapy techniques .but the improvement and recovery to normal shape will be dependent on time period since the deformity has occured. so dont delay the issue.non reversible types can be managed by splinting ,plaster cast or surgical correction.

Its mallet finger do wax therapy and ultrasonic therapy for few days and extension exercise according physio if it will work then OK otherwise surgery in further process

Medicine will not help in correcting the deformity,it will only control the pain...better would be take physiotherapy treatment which will help in maintaining the mobilty of the joints and also improve the muscular strength.Wax therapy as well joint mobilisation and stretching by a therapist along with taping/splinting will help.