I started smoking in january n i stoped.3 weeks ago could i have throat cancer

Sounds like phobias: Cancer from smoking generally requires decades (not months) of smoking. It sounds to me like an unnatural fear or phobia. If it is worrying you, see your doctor and/or get a referral for an ENT physician to exam you for reassurance. If you still have this fear, talking to a therapist/counselor may be helpful. Congratulations on stopping. Keep it that way and good luck!!!