Why is there always Nandi in front of Shiva linga in Shiva Temple. And only behind Nandi, that we should bow, prostrate and look to Shiva by the two horns of Nandi.
According to methodological stories :
When the positive forces, the devas, and the negative forces, the asuras, joined together on a rare occasion to churn the ocean with a mountain to obtain the nectar of immortality they utilized Vasuki, the serpent, as the rope.
The devas pulled from one end and the asuras from the other. Lots of precious herbs and gems were produced during the churning and one of them was a poison ( halahala ) which became human karma. This “poison” was so dangerous that none of the devas or asuras wanted to go near it. It was extremely sticky and coming into contact with this poison, i.e., human karma, would drag the divinity down to the realms of human suffering and ego.
As everyone else ran away, Lord Siva, followed by Nandi, came forward to help as he was the only one who could counteract this deadly poison. Siva took the poison into his hand and drank it, the descent of the poison was in turn stopped at His throat,by His divine consort. Siva is therefore also known as Neelakaṇṭha (the blue-throated one) and Viṣhakantha (the poison-throated one).
The poison in the throat is always a burning sensation for lord Shiva. Lord Shiva loves to spend time in meditation (Dhyanam). But this burning throat is not allowing him to do his meditation. Then he ordered Nandi to sit in front of him and blow some air on to his throat. The air blown on to his throat relieves him from the burning sensation. From then onwards,Lord Shiva does his mediation with the help of Nandi.
This is the story behind having Nandi sitting in front of Lord Shiva in all our temples.
Whenever we visit Lord Shiva temple we should not go in between Nandi and Shiva lingam (we should not break the path between Shiva and Nandi). If we do so, people say that we are disturbing Lord Shiva’s meditation.
If we have a wish to share with lord Shiva, we should tell the wish in the ears of Nandi. Nandi later shares the wishes of visitors with Shiva after the meditation.