According to picture it may be due to minor salivary gland disorders. Though clinical evaluation is needed . you need not to worry If painless and not rapid growing.most of the time it resolve spontaneously.
Next Steps
1)intake plenty of water
2)warm salt water mouth gargle 3-4 times daily
3)suck sour lemon or
sugar free lemon candy to increase salivary flow
Health Tips
if it is increasing in size or number or becoming painful and not resolved after 1month ,visit nearby dental clinics