Malbim: They stop me from attaining the ultimate, final happiness. Plagues that affect the body, they stop it from attaining perfection. As long as the Nefesh is incarcerated in physicality, it feels pain and its occurrences. Your blows harm not only the body - I would not be pained over this - rather, also the Nefesh, which is the primary part of the person.

Radak: It is the plague that You put on me. The suffix Chaf (your) can refer to the one who acted, or the one acted upon.

Malbim: There are two kinds of Nega'im. (a) Some are essential due to man's physical substance, or the nature of the world. Refer to 39:11:3:3, 39:12:2:1.

Rashi citing Menachem: It is fear of Your blows. Tigras is an expression of fear, like "va'Yagar Mo'av" (Bamidbar 22:3). Tov is part of the root; sometimes it is omitted, like we find in Tenuvah and Telunah ¹ .

Rashi: Tigras is [an expression of conflict,] like "Sisgareh b'Ra'ah" (Divrei ha'Yamim II, 25:19), "Al Tisgaru Vam" (Devarim 2:5). The verb is Gareh, just like from Kaveh, Aveh and Tzivah, the actions are Tikvah, Ta'avah and Mitzvah. From Your hand's blow on me, I was finished off.

Malbim: They are due to the conflict of Your hand and actions, i.e. the [four] elements. Man is composed of matters with conflicting natures.