Learn Croatian: Nemam ni flaster ni gazu za ogrebotinu. - I have neither a plaster nor gauze for the scratch.

Croatian requires double negation. When you use the conjunction ni... ni... (neither... nor...), the main verb of the sentence must also be negative. You are literally saying "I do not have neither a plaster nor gauze."

I learned that the verb nemati (not to have) takes the genitive case. Why are the objects here in the accusative?

While nemati often triggers the genitive of negation, especially for uncountable or abstract nouns (like nemam vremena), modern spoken Croatian frequently uses the accusative for specific, physical objects. Saying ni flastera ni gaze in the genitive would also be correct, but the accusative used here is very common and natural.

Why does flaster look like a nominative word while gazu clearly has an accusative ending?

Both words are actually in the accusative case because they are direct objects. Gaza is a feminine noun, so its ending changes to -u. However, flaster is a masculine inanimate noun, and the accusative form of masculine inanimate nouns is identical to their nominative form.

Why is the word for scratch (ogrebotina) in the accusative case (ogrebotinu) here?