My son (10yrs

Your son ought to be seen by a dentist as soon as possible. The open dentine surface protected and if possible a tooth coloured filling placed to restore his 'dignity'.
The tooth must be regularly monitored to check that the nerve has not been damaged by the accident
Perhaps at a future date in ( when he is 18 - 21 ) a porcelain veneer or cover can be used to restore the tooth. There are many adults who have successful tooth coloured fillings which have been in place for 15 years or more following a childhood accident

I would recommend that you take your son to see a dentist as soon as possible to examine the tooth in detail.

The immediate aim would be to treat the tooth as gently as possible to minimise any further stress to the nerve. Emergency treatment would be to seal the exposed dentine with either glass ionomer cement or a dentine bonding agent. To get a good result will require a co-operative patient to restore the fracture with composite white filling.
This can be a permanent solution although may need redoing from time to time as it can fracture or discolour. When your son reaches 18 it would be possible to place an 0.2mm thick "enamel shell" porcelain veneer over the fractured portion
the important thing is to do the least intervention necessary and monitor the health of the nerve within the tooth

This site is useful in determining the best way to treat any dental trauma situation
www.dentaltraumaguide.org/Trauma_Pathfinder.aspx

I would agree with Dr Mandon-Gassman's answer. Composite bonding is the best treatment for now and even possibly long term but a veneer could be an option when your son is older
It is also important to have an xray so the health of the nerve can be reviewed over time