All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is unlawful to throw the pebbles (Jimaar) during the days of Tashreeq (11th, 12th, and 13th of Thul-Hijjah) before midday and any person who did that, his throwing of pebbles is invalid. If the person repeats the throwing of pebbles in time, then he does not have to do anything because his last throwing of pebbles is valid. But if the person fails to repeat the throwing of pebbles in time, then he has to offer a sacrifice (slaughter a sheep).
This is the opinion of the majority of scholars except Abu Haneefah who disagrees with it. The evidence of the scholars is the sound Hadeeth reported by Muslim from Jaabir Ibn Abdullah who said that the Propheet threw the pebbles on the Day of Sacrifice (10th of Thul-Hijjah) after sunrise (before midday) as for the following days he threw the pebbles after the sun had passed the meridian (after midday).
For the above, we advise this brother that if he was sure that he threw the pebbles before Midday to slaughter a sheep and distribute its meat among the poor people around the Haram in Makkah or to ask someone to do that on his behalf if he cannot do it himself.
Allah knows best.