Hi Jiawei, All these words can have different meanings, depending on the context. But let's stick to comparing these three with each other. Someone who feels nervous has a feeling of unease or apprehension, like before takeoff when travelling by plane. When you are excessively nervous, for example, a child on the first day of school or an adult on his first day at his new job, then you could say that you are anxious. Being tense is a state where your muscles are tight when you are filled with nervousness and anxiety, not being able to relax. When a student is about to take his IELTS exam, he may feel so nervous that his neck and shoulder muscles become tight or tense. Someone tense may easily jump up when he hears a sudden noise. I hope this helps a bit.

Estar nervioso es puntual ante una situación concreta en la que cualquier persona se sentiría nerviosa, es decir, es una situación en la que todos sentiríamos síntomas de nerviosismo, ya sea porque fuéramos evaluados por otros o implicara algún peligro real para nosotros. A diferencia de estar nervioso, el estado ansioso implica ideas de catastrofización y muchos pensamientos negativos relacionados con la salud. En el caso de sentirse tenso, estar es en estado de tensión física, moral o espiritual. por ejemplo cuando alguien te está presionando y te tranca (no es como el estrés)