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.
The question is not clear, but in general, we say: If this gold has reached the Nisaab (minimum amount liable for zakaah), which is approximately eighty-five grams of pure gold, then it is obligatory to pay zakaah on it every lunar (Hijri) year. So if you did not pay zakaah on it, then you must hasten to do so.
As regards selling your gold now or waiting until its price increases, then this is up to you. However, since you intended to give its price in charity, then it is better to sell it without waiting as a means of hastening to do good deeds.
Giving this charity is not obligatory on you just because you had the intention to do so, but charity is one of the best deeds.
For more benefit on the zakaah on gold and jewelry, please refer to fatwas 83665 and 82925.
Allah knows best.