Snot
Boogers
noun
Maybe you didn't know this, but if you're like everyone else learning a new language, you learn the cuss words first. くそ is sh*t / garbage, though it's not really a "bad" word in Japanese like it is in English. So, what is your nose sh*t? It's your snot and boogers. Ewwww, stop eating them!
The reading is just like what you learned with the kanji. はなくそ.
鼻くそ、指でほじるとかありえないんだけど。ティッシュ使って取りなよ。
Picking your nose with your fingers is unthinkable. Use Kleenex to clean it up.
電車で鼻くそをほじってこねてる女の人を見てしまい、気分が悪くなりました。
I felt nauseous after seeing a woman picking her nose and playing with her boogers on the train.
三才の息子が鼻くそを食べるので、「マナーが悪いよ！」と注意したら、食べる前に「いただきます」と言うようになりました。
After I scolded my three-year-old son for eating boogers and told him it was bad manners, he started saying "itadakimasu" before eating them.