Hi there! I’m a green witch but I graduated from a Liberal arts university and have studied and been to many countries with ancient deities. I have a couple of questions if you’re still seeking. Did you dream about this deity only once or has it recurred? Did it feel like it was a positive energy or neutral or that the deity was reaching out or seeking you? Or, did it feel negative, icky or weird - is that why you are stuck on it? Even today I would write down every single little thing you can think about the dream. All the things others have said here resonate and are really good to do.
If your dream was general about 4 armed deities it may be more general than a specific deity making contact. Interestingly, Plato wrote in The Symposium that ….”according to Greek mythology, humans were originally created with four arms, four legs and a head with two faces. Fearing their power, Zeus split them into two separate parts, condemning them to spend their lives in search of their other halves.” — This could mean something if you are in ‘search of your other half’ - food for thought at least? 
Deitys are easily spotted in Indian depictions from various times. Ganesha, Lakshmi and Vishnu are probably the most popular and I believe @Amaris_Bane mentioned them already. Below is a cursory depiction of them.
Ganesha
Ganesha is the elephant-headed son of Shiva, one of the three most important deities of the Hindu pantheon, and his consort, the goddess Parvati. He is widely worshiped as the remover of obstacles and the bestower of good fortune, prosperity, and health.
Lakshmi
Lakshmi is commonly portrayed as a beautiful woman with four arms, standing on a lotus flower. There is usually one, or sometimes two elephants behind her, anointing her with water. She is often depicted sitting beneath Vishnu, massaging his feet.
Mishnu, Kali are also and there are many lesser known ones as well.
Every Hindu god with many arms has multiple qualities which are represented by their different hands. It shows the immense strength and power of the Gods. Multiple hands also show that they can perform numerous tasks at a single time. Most Deities have four hands and some of them also have ten or twenty hands.
Greek Pantheon:
The Actiorione, Siamese twins and sons of Poseidon. They had four arms, four legs and two heads.
Hephaestus, God of fire, metalworking, stone masonry, forges, the art of sculpture, technology, and blacksmith.
I’d say there are tons more in Buddhism and even other cultures. If any of these rings a bell, practice with your pendulum as @Amaris_Bane laid out, else, the links that @MeganB will also shed light if you are drawn to them.
I hope you find what you seek - let us know!! 