Hello, yeah, these things are better to plan ahead honestly, there's a whole process to import goods... specially medicine to another country.
The due process is for you to contact a customs broker (agente aduanal), many options, you can google them, can't recommend any. With the customs broker you will do a DUA (Declaración Unica Aduanera) (Customs declaration) where you will basically list the amount of medicine, it's price, characteristics, weight, your personal info as importer, transport info, etc.
With it, your customs broker will have to ask for a VUCE authorization from the Health department, once they clear it (usually within 2 days) you're able to pay for your cargo and take it with you. In this step you can also ask for a tax exoneration if you think your non profit organization and cargo qualifies for it.
If you didn't do any of these and show up at the airport with the medicine, if customs officials inspect your luggage and find it they will most likely retain your bags, if you didn't declare it you could be fined (very unlikely) and you will have up to 6 months to do this procces if you want to get your bags back.
I appreciate what you're doing to help and your charitable work, and I know this is a pain, but this is mainly done to keep our country safe, specially with medicine, health department has to inspect if the medicine is out of date, if it's allowed, if it's not a danger to our people, etc.