Is it normal to have a swollen meatus after masturbation? I'm uncircumcised

Not likely a problem. The meatus can become irritated with sexual manipulation, particularly if the frenulum of the intact foreskin pulls on it as it is retracted. See your md if it causes symptoms.
Meatus. The urethral meatus is lined with urothelium and the glands is lined with keratinized epithelium. The meatus is much ore sensative and can be irritated much more easily by creams or ointments.