Hobbes does address the idea of justice when speaking about Natural Law, however, justice enters only at a tertiary level. The primary components of Natural Law allow for neither justice nor injustice as every individual is said to be in a warring state with every other individual for full possession of goods and full dominance of territory. Hobbes says that primary passion and reason combine to compel individuals to seek a pleasant life (passion) and peace as know from "the laws of nature" (reason), thus driving him to seek contracts for secondary civility and escape from warring. Justice enters at the tertiary level as these contracts require enforcing through the offices of an agreed upon governing power.
The first law of nature, according to Hobbes, is thus to seek peace.
The second law of nature is thus to seek contracts of peaceful accord.
The third law of nature is then to honor and keep the contracts by governing against the injustice of violating contracts and encouraging the justice of keeping contracts.