As a Noun:
1. The feeling of worry and tenseness because of difficulties in your life. English = anxiety, stress.
2. A small worry or doubt that you keep thinking about. English = niggle.
3. Something that is not understood or known about, causing you to think about it a lot. English = mystery.
As a Verb or Adjective:
1. To feel worried and tense because of difficulties in your life. English = (be) stressed, (be) anxious. Idiomatic English = (be) sick with worry, worry yourself sick.
2. To feel nervous or worried before performing on stage or doing something in public. Idiomatic English = have butterflies in your stomach.
3. To feel slightly worried or doubt something over a long time; to not understand or be confused by something over a long time English = (be) niggled; (be) puzzled.
4. To make someone feel slightly worried or confused about something for a long time. English = niggle, puzzle.