The word nostomania is not a hard word to figure out; if you don't know what it means, study the word for a moment, and see if you can suss out its meaning.
Here's a hint: split the word between the "o" and the "m."
The second half, "mania," is easy to figure out; "mania" is a form of mental illness marked by excessive excitement, euphoria, or activity.
To figure out the first half, ask yourself what words you know that begin with the syllable "nost." If you thought "Nostradamus," you picked the wrong one. "Nostalgia" is the word you're looking for. Nostalgia is a longing for a time or place which has happy associations.
Put those two things together, and you have excessive longing over a time or place with happy associations.
Now we just need to tweak the definition a bit; "nostomania" is all about a place with happy associations: home.
So "nostomania" is an excessive longing to return home. Or, to put it another way, it is extreme homesickness.
Example: Even though the camp had many fun activities, nostomania kept Joey from enjoying any of them.