Answer

If you mean “Nigod ayushya tap”, it is not a standard single, separate tapa in Jain Dharma. Nigod refers to a very subtle/common-body form of life, and āyushya is the karma that determines life-span. Jain tapasya is traditionally explained as 12 austerities: 6 बाह्य (external) and 6 आभ्यंतर (internal). ( jainbelief.com)

Explanation

In practical Jain teaching, tapasya is done through the usual austerities, such as anashan (fasting), unodari (eating less), vrittisankshep (limiting food/items), rasatyag (giving up tasty foods), kayaklesha (enduring bodily hardship), and samlinata (restraint of the body); and internally through prāyashchitta (repentance), vinay (humility), veyavachcha (service), swādhyāya (scriptural study), dhyān (meditation), and vyutsarga (letting go). These are the classical ways of nirjarā—shedding karma. ( jainworld.jainworld.com)

Spiritual Understanding

So, if your question is how to “do” a penance related to avoiding lower karmic states, the Jain answer is: not by a ritual called nigod ayushya, but by discipline, restraint, repentance, study, meditation, and guided tapasya. The aim is purification of the soul and reduction of karmic bondage, especially with the help of a qualified Guru when undertaking stronger austerities. ( jainworld.jainworld.com)

Takeaway

Nigod is a life-state, not a tapa. Ayushya is lifespan karma. The proper Jain path is to practice the 12 tapas in the right way and with right intention. ( jainbelief.com)