I dont really have advice here - dont know what to do. But as your son doesnt suck his thumb all through the night, it may not have such an effect on his teeth.
But never ever give an under 1 year old honey, as suggested in a previous answer.
"Honey sometimes contains a spore of the bacterium Clostridium Botulinum. This can cause a rare form of food poisoning (botulism) in babies and, very occasionally, in adults. Babies under six months are most vulnerable. The symptoms of botulism appear around eight to 36 hours after consuming the honey or other contaminated food. Symptoms may include constipation, listlessness and lack of appetite. If you suspect your baby may be affected, seek medical help straight away. Although cases of botulism in babies are very rare, it is recommended that you don't give your baby honey until after his first birthday.
Another reason not to add honey or sugar to your baby's foods and drinks is because they can harm his teeth and may also give him a 'sweet tooth'. If, however, you do choose to add something sweet, then fruit juice, puréed fruit, mashed banana or dried fruit make good alternative sweeteners.
Good dental hygiene is important as soon as your baby's first tooth appears, and this includes regular brushing. Use a trainer cup rather than a bottle from six months, and offer sweet foods as part of a meal, rather than in between meals. Regular check ups with a dentist are also recommended."