A thorn in the flesh.
More Hungarian Proverbs:
He who is conceited, will easily be ashamed.Hungarian
He reads between the lines.
Hungarian
If you don't cherish the little, you don't deserve the more.
Hungarian
Even if the wound is healed, the scar of it remains.
Hungarian
Every man should practise only his trade.
Hungarian
The trees do not grow up to the sky.
Hungarian