tired again
Dogs mouths have one of the highest bacterial content of mammals. Blood poisoning is common. watch for a red streak developing down the inside of the thumb. If at anytime you see this streak or have pain spreading down into the palm go to the ER right away as blood poisoning can spread rapidly. Soak thumb in warm water and keep bite area coated with a triple antibiotic ointment like polysporin and use a bandaide to protect from dirt.
I accidentally pricked my finger on my partial plate about 10 years ago and developed the red streak within 24 hours and went to the ER. Dr. said human mouths are very heavy with bacteria (only dog is worse/per the dr.). That treat numerous cases each year in mothers who have been bitten by teething or ill mannered infants.
Has your dog have rabies shots? My brother and I raised hunting dogs got many years and that is very unusual behavior for a beagle. I would take him to the vet. Many conditions can cause irritability in dogs which will cause them to lash out.