Googling around someone briefly mentioned H.P Lovecraft but didn't seem sure of it.

There is no evidence from his letters or any later anecdotes or memoirs that Tolkien read Lovecraft. While some folks have argued that the Dweller in the Pool is a very Lovecraftian entity, there's just no direct evidence to suggest Tolkien ever read Lovecraft (he did read Robert E. Howard, but that was after he wrote The Lord of the Rings).

In fact we know relatively little of Tolkien's readings in popular literature and fantasy in general. To refer back to u/Zeuvembie, we do know that Tolkien read Lord Dunsany, but if you look at How Elves Were Depicted Before The Lord of the Rings, it's hard to say that Tolkien borrowed anything directly from Dunsany in terms of concept or style - he certainly might have, since Tolkien ended up creating his own mythology just as Dunsany did, but then you've got two literate Englishmen working in the realm of fantasy and worldbuilding at overlapping periods, so there's almost bound to be some correlations.

Douglas A. Anderson in Tales Before Tolkien points out a number of fantaisists that preceded tolkien and might have influenced his work, including Arthur Machen, George MacDonald, James Branch Cabell, Andrew Lang, H. Rider Haggard, and William Morris, all of whom may have influenced Tolkien to some degree; Anderson points out:

The roots of fantasy extend back to Homer's Iliad and Odyssey and on through the medieval literatures that were Tolkien's specialities as a professor at Oxford. The Anglo-Saxon poem Beowulf, which concerns a hero and his fight with monsters (including a dragon); the Arthurian romances, including Sir Gawain and the Green Knight (which Tolkien edited in Middle English and also translated), and those by chretien de Troyes; the medieval legends of Alexander the Great (who discovered the Trees of the Sun and Moon in the Far East, the inspiration of Tolkien's two Trees in Valinor); and the Icelandic Eddas and sagas, these are the cornerstones of the medieval genre of heroic romance, with heroic exploits, quests, interlaced stories, and various intrusions of something beyond the natural--that is, elements of fantasy. Tolk himself followed in this tradition, and The Lord of the Rings, as its author rightly noted, is more properly called heroic romance than a novel.

Anderson, who is a great Tolkien scholar, adds notes to the various stories in how they or the authors influenced Tolkien, and there is more to dig into the subject if you care to dig - Tolkien scholarship being its own sub-field at this point, that is where I recommend you start if you're interested in learning more.

To give another example: the sword Gurthang in the Silmarillion (and the tale of Túrin Turambar) has its origins in the Volsung Saga and Nibelunglied, which also inspired Poul Anderson's The Broken Sword (which in turn inspired Michael Moorcock's Elric of Melniboné, which in turn inspired the Sword of Life Stealing in Dungeons & Dragons, etc.)

Related to your question, you might like to look at u/AncientHistory's answer for What was fantasy literature like before Tolkien, and how does it compare to Tolkien's works?