For something like that that's actually forgetting a rule rather than making a valid choice that you later regret, just correct it as soon as you notice. By my calculations, however, you spent it already. Your non-intelligence stats:
Code:
Stat value base cost
Str 8 10 2
Dex 14 14 6
Con 12 12 4
Wis 14 14 6
Cha 14 14 6
With 32 point buy, that leaves 8 points for intelligence, enough for a base score of 15. Your gray elf bonus brings it to 17, stat bumps at 4th, 8th, and 12th level make it 20, and your newly upgraded headband brings the total to 26.