Less serious Implanon side effects may include:
pain, numbness, or tingling where the implant was inserted;
minor bleeding or scarring where the implant was inserted;
menstrual cramps, changes in your menstrual periods;
mild headache, dizziness, mood changes;
vaginal itching or discharge;
breast pain;
acne;
problems with contact lenses;
nausea, mild stomach pain;
back pain;
feeling nervous or depressed;
sore throat, flu symptoms; or
weight gain.