I had something very similar back in February and was on the verge of visiting casualty. Side of my face was out to the extent of about half a tennis ball and I swear I'd rather have toothache.
It was a Saturday, so braved it out with a mix of Ibuprofen and alcohol (but since your lad's just 9, not something I recommend) and saw my doctor on the Monday. She diagnosed an infection and gave me antibiotic tablets because the ear was too swollen for drops, and it began to clear within the day.
I had been putting olive oil in earlier in the week because I had thought it was just a mild earache caused by a wax build up. I was told it probably hadn't been a good idea, because anything like that you put in there can exacerbate the infection - especially since there wasn't much wax in there to begin with so it had been a totally useless exercise in any case.
Lesson learned and now the only thing that goes in my ears is swimplugs.
I suggest a trip to the GP asap if it's still no better in the morning. You wouldn't want him being ill on holiday, and kids' ears can be so easily damaged.