Get yourself some magical help.
I won't list every spell that can help you in your situation, but you should be looking at spells that can either produce light (Light, Daylight, Continual Flame, etc) , give you Darkvision, or light up an enemy (Faerie Fire). Depending on your party's setup, there is a very likely chance that you will have at least one of those, as they are available very early in the game.
Magical Items can help too
In addition to spells, there are a bunch of magical items listed in the DMG that could shed light on your situation (sorry...), ask your DM if you can maybe go on a side quest to find one of these. Some examples include: Goggles of Night, Driftglobe, Sunblade.
D&D's underdark flora can help as well
Out of the Abyss, an adventure module set almost entirely in the Underdark, offers some interesting fungi that naturally grow deep underneath the earth, away from the sun. The module is also set in the Forgotten Realms, so "underdark fungi" might not be a thing in your DM's setting, ask your GM if you can find some of the fungi below (you can find more details in page 23 of Out of the Abyss):
A one-to two-foot-tall mushroom with a combustible cap, a single torchstalk burns for 24 hours once lit.
To a lesser extent:
A nightlight is a tall and tube-shaped bioluminescent mushroom that grows to a height of 1d6+4 feet and emits bright light in a 15-foot radius and dim light for an additional 15 feet. A night light that is uprooted or destroted goes dark after 1 round.
A bioluminscent green moss that grows in warm and damp areas [...] It sheds dim light in a 5-foot radius, and can be harvested, dried, and made into a phosphorescent powder or pigment.