The readings are the kun'yomi vocab readings. With 鼻 you learned that with the kanji. With 先 you learned that with the vocab. So, you should have all the pieces to be able to read this. Remember, body parts tend to change words into kun'yomi readings for some reason, no exception here.
You got mustard at the tip of your nose.
That police dog started twitching the tip of its nose and sniffing at the stranger.
When Fugu saw that the tip of Salmon’s nose was so red, he found it very cute.